Цитата(tig81 @ 5.2.2009, 0:23) *

((cos^3 t)^(-1))'=(-1)*((cos^3 t)^(-1-1))*(cos^3 t)'=...

=sin^3 t/cos^6 t

Цитата(Vladi @ 5.2.2009, 0:26) *

=sin^3 t/cos^6 t

-sin^3 t(t)'/-(cos^3 t)^2=sin^3 t/(cos^3 t)^2

Цитата(Vladi @ 5.2.2009, 0:30) *

=sin^3 t/cos^6 t
-sin^3 t(t)'/-(cos^3 t)^2=sin^3 t/(cos^3 t)^2

=tg^3 t/cos^3 t